Self-pressurized (aerosol) dispensers for the testing of smoke detectors have been marketed for decades. They were originally formulated with about 1 to 4% by weight of some proprietary ingredient and 96% to 99% by weight of a totally or essentially non-flammable propellant such as CFC-12 (dichlorodifluoromethane). When all the CFC aerosol propellants were banned as of 1 Apr. 1978 the fledgling smoke detector tester industry was forced to use either an essentially non-flammable blend of HCFCs (hydrochlorofluorocarbons) or the intensely flammable hydrocarbon propellants, such as propane and iso-butane. The HCFC propellants were banned in 1990, leaving the industry with no other recourse than to use the hydrocarbon propellants.
In 1995 DuPont commercialized totally non-flammable HFC-134a (1,1,1,2-tetrafluoroethane), primarily as a replacement for the CFC-12, still permitted for use in MDIs (Metered Dose Inhalants). Most marketers of smoke detector tester aerosols began to use this new propellant, since it was safer to use in environments where free flames or electrical sparks could be present and cause ignition of the spray. However, HFC-134a is a remarkably poor solvent, and some marketers included up to about 20% by weight of ethanol in their formulas as a co-solvent to solubilize their various “synthetic smoke” active ingredients. Some of these formulas then became marginally flammable—unable to pass standard gas-air flammability tests.
During the late 1990s HFC-134a was accused of having a large GWP (global warming potential). It was shown to be about 1350 times more potent than carbon dioxide in this respect. Under the increasingly critical demeanor of the United States Environmental Protection Agency (“U.S.EPA”) and several non-governmental organizations (“NGOs”), HFC-134a suppliers created inter-disciplinary committees that would either approve, approve in limited quantities, or disapprove the sale of this product to marketers, according to product type, annual consumption and other factors. Companies manufacturing products demonstrating health and life safety attributes had the best chance of obtaining HFC-134a. On that basis firms marketing smoke detector testers were permitted to use HFC-134a, while applications by most others were rejected.
In 2008 the State of California passed Senate Bill SA-32 into law. SA-32 was designed to either eliminate or minimize the use of substances demonstrating a significant global warming potential (such as HFC-134a) on an urgent basis. The charge of implementing SA-32 was assigned to California Air Resources Board (“CARB”) by Governor Arnold Schwarzenegger. According to Consumer Specialty Products Association (“CSPA”) documents CARB has now banned about 85% of the annual tonnage of HFC-134a used in California for duster aerosols. This has caused the affected marketers to reformulate, typically replacing the HFC-134a with HFC-152a (1,1-difluoroethane), which is flammable, but with less intensity than the flammability of the hydrocarbon propellants, such as propane and iso-butane blends.
Meanwhile, the U.S.EPA is slowly developing a very complex program for the step-wise reduction of HFC-134a and similar “high global warmer” gas-liquids, typically used in aerosols, air-conditioner and freezer coolants, foamants and other products, unless exempted. The U.S.EPA has announced that their first reduction, to about 83% of the tonnage used in their reference year of 2005, will be finalized soon. Further reductions will follow, ultimately leading to a complete phase out.
Until quite recently this left the marketers of smoke detector tester aerosols in a difficult position, since only the intensely flammable hydrocarbon propellants could be used without present or future restraints. Since industrial smoke detectors are sometimes located in areas where free flames and spark producing electrical motors, switches and similar equipment are present the spraying of aerosol formulations typically containing 96 to 99% by weight of intensely flammable hydrocarbon propellants could create a considerable risk to life safety.
For completeness, there is another propellant, called dimethyl ether, which is also quite flammable. It is a very strong solvent and has not been seriously considered for smoke detector testers due to concerns about its ability to gradually erode plastic components of the detector.
During the year 2010 the aerosol industry recognized that Honeywell Fluorine Products was developing a new, non-flammable aerosol propellant. On or about May 8, 2011, an article in the ST&M (Spray Technology and Marketing) journal provided documentation. The propellant was HFO1234ze(E) (trans 1,3,3,3-tetrafluoroprop-1-ene) having a negligible GWP and almost completely non-flammable. It was particularly offered as a replacement for HFC-134a and HFC-152a used in duster aerosols, where it would constitute from about 99.5 to 100.0% of these formulas. It has been considered as an essential formula ingredient of the subject invention, if modified so that it would become totally non-flammable.
US regulators have a long history of applying certain test procedures and pass/fail criteria to aerosols, primarily used for the warning labels of aerosols and marking of outer shipping cartons. For example, the Flame Propagation Test, used by the United States Consumer Products Safety Commission (“U.S.CPSC”), the U.S.EPA, and the United States Department of Transportation (“U.S.DOT”) (formerly), requires that the aerosol be first equilibrated to 70° F., and then sprayed through the top third of a candle flame from a distance of six inches. If the spray ignites, forming a fire plume longer than 18 inches from the candle, then dispensers of that product must be labeled as “Flammable,” provided they are larger than four fluid ounces (118.2 mL) in capacity. This does not mean that products passing this test may be labeled as “Non-Flammable”. Quite often they may have a lesser degree of intrinsic flammability.
A second test is the Closed Drum Test (in Europe, the Enclosed Space Test). While currently obsolete in the USA, it is currently used in Europe, Japan, by other nations, and by certain international transportation organizations, such as International Maritime Consultative Organization (“IMCO”). In the interest of global harmonization of aerosol labeling and shipping, both the (Federation of European Aerosol Associations—17 countries) and the United Nations are seeking to re-establish this test in the USA. The test consists of spraying a fixed amount of the aerosol product into a 55 U.S. gallon steel drum or similar vessel, which contains a lit candle or gas burner. One end of the drum is covered with a thin film of polyethylene. If the Lower Flammable Limit (“LFL”) is reached, a large volume of flame will be produced, normally accompanied by a “whooshing” sound and with heat and pressure sufficient to rupture the film. Here again there will be aerosol products that will pass the test, but would fail it if more product had entered the drum. Aerosols that pass the test must not be labeled as “Non-Flammable”, but may be labeled as “Non-Flammable by the Closed Drum Test”, or the equivalent. Even these modified warnings can lead to consumer confusion and possible misuse of the product.
A listing of the official aerosol flammability tests, including those described above, is presented as follows:    The Flame Propagation Test.    The Flashback Test.            The Closed Drum Test.            The Ignition Distance Test (Europe and U.N.).    The Enclosed Space Test (Europe and U.N.)    The Foam Flammability Test (Europe and U.N.)    The U.S. CPSC Open Cup Flash Point Test.    The U.S.EPA Open Cup Flash Point Test.    Other tests have been published, such as the Closed Cup Flash Point test and the 200° C. Preheated Hot Plate Spray Test, but they have no official sanction.
All of these tests are used to differentiate aerosols by their relative flammability. None of the tests, individually or in concert, can be used to qualify an aerosol product as “Totally Non-flammable”, “Almost Completely Non-Flammable” or “Non-Flammable”. However, in the USA and Canada there are no laws or regulations that would prevent an over-zealous marketer from marking his aerosol product as “Non-Flammable” or the equivalent, provided it passes that country's applicable, official tests. The primary deterrent for companies marketing such products is being accused of “failure to warn” or “misleading labeling” in the event of an accident. A secondary deterrent is that the U.S.FTC (U.S. Federal Trade Commission) may consider such products to be labeled with a false advertising statements.
In the USA the only test for establishing “Non-Flammability” is the ASTM E-681 (American Society for Testing Materials, Method E-681) assay. The procedure utilizes a five liter (c.a. 1.2 U.S. gallon) flask with an enclosed sparking device. Precisely measured amounts of the aerosol product are introduced, with intermittent operation of the sparking unit. If no flame propagation occurs the product is deemed “Non-Flammable”. The test is typically conducted at 68° F. Flammability is said to occur if a flame is produced that reaches the wall of the container. It must also exhibit an angle of greater than 90° from the spark source. These effects must occur at a gas concentration of less than 12 volume-percent for the product to be considered “Flammable”. The term “gas”, as used in this test, means a fluid with a boiling point of 68° F. or lower, under an atmospheric condition of 760 mm. of mercury absolute pressure.
The lowest concentration of gas that produces the above flame propagation is recorded as the LFL. The highest concentration of gas that still produces the above flame is recorded as the Upper Flammable Limit (“UFL”). The terms LEL and UEL are often used interchangeably with LFL and UFL, resp. The “E” stands for “Explosive”. The “window of flammability” between the LFL and UFL is described as the “vapor flame limits” or “flammable range”. Gases that exhibit a flammable range at 68° F. are considered to be “Flammable” by this test. Conversely, a gas that fails to exhibit an LFL and UFL at 68° F. by this test is considered as “Non-Flammable”.
The European counterpart to the ASTM E-681 is the EU A11 test. The apparatus consists of a two-inch inside diameter by 12 inch long glass tube with an internal ignition source composed of an electrical sparking device that lights a match. The assessment criteria are similar to those that are applied to the ASTM E-681 method.
As is known to those skilled in this area, the flammable proclivity of gases increases as the temperature increases, as the pressure is increased, and sometimes changes as gaseous impurities are added or increased. To our knowledge and belief no information has been published regarding the effect, if any, of adding an essentially non-volatile liquid to the test aerosol dispenser. As a classic example of the pressure effect, HFC-134a is totally non-flammable at 68° F. and 760 mm mercury absolute pressure. But at 68° F. and a pressure of about 1550 mm mercury absolute (15 psi-gauge) it displays a flammable range starting at about 7.5 volume-percent gas.
To more fully define the flammability profile of their HFO1234ze(E) propellant Honeywell tested it using both the ASTM E-681 and European EU A11 test methods. Testing was also performed at several temperatures. The USA testing was conducted by Honeywell, while the European method of testing was done by Chilworth Technology U.K. (in England), a highly regarded flammability testing firm. Results were provided by Honeywell as follows:
Method ASTM E-681    At 68° F. No flammability. (No LFL or UFL.)    At 86° F. LFL=7.7 volume-% and UFL=8.7 volume-%.    At 140° F. LFL=5.8 volume-% and UFL=11.3 volume-%.    At 212° F. LFL=5.8 volume-% and UFL=11.8 volume-%.
Method EU A11    At 73° F. No flammability. (No LFL or UFL.)    At 212° F. LFL=7 volume-% and UFL=12 volume-%
FIG. 1 is a graphic representation of the above test results, which is hereby made a part of this patent application. Specifically, FIG. 1 shows that propellant HFO1234ze(E) can produce a potentially flammable gas-air mixture above a temperature of about 79° F. when tested by a standard method identified as ASTM E-681. In the graph (100) indicates the LFL arm, while (101) indicates the UFL. The area enclosed by the parabolic graph contains flammable gas-air compositions at the indicated temperatures. (102) depicts a typical experimental result. There are four of these on the graph and two more are indicated at higher temperatures. (103) indicates that all gas-air compositions below about 79° F. are non-flammable.
One may conclude from this rather intensive testing that Honeywell's HFO1234ze(E) begins to develop a flammable range at about 79 to 80° F. The range rapidly increases with rising temperature.
Whenever an aerosol is sprayed the gaseous content of the spray becomes increasingly diluted with ambient air. The gas concentration ranges from essentially 100% at or very close to the spray actuator terminal orifice, moving ultimately down to essentially 0% when fully diluted with air. During the spraying episode some parts of the spray may be ephemerally diluted into the critical area such as of from 7.7 to 8.7 volume-percent at 86° F. If the temperature is 80° F. or higher, and a suitable ignition source is present, then a flammable event becomes possible, perhaps with serious consequences. The relative fire hazard increases at higher temperatures, since the flammability range broadens
Further limitations and disadvantages of conventional and traditional aerosol systems will become apparent to one of ordinary skill in the art through comparison of such systems with the present invention described herein.